Process for the production of magnetic materials in powdered form



June 27, 1933. E. scHUMAcHER Er AL 1,915,386

PROCESS FOR THE PRODUQTION 0F MAGNETIC MATERIALS IN-POWDERED FORM Filed April 16, 1932 .i S @si ko mais.

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Patented June 27, 1933 UNITED STATES PATENT or-'Flcs :ABLE E. BOHUIACHER, OF HAPLRWOOD, NEW JERSEY, AND WILLIAI O. ELLIS, OB IALV'ERNE, NEW YORK, ASBIGNORS TO BELL TELEPHONE LABORATORIES, INCOR- PORATED, OF m YORK, N. Y., A CORPORATION OF NEW' YORK Incense ron 'rmi raonUc'rIcN or mamario Hermanns nr rownmm :vom

Applicatlon'led April 16, 1932. lerial Re. 805,744.

The present invention relates to the production of magnetic materials and more particularly to methods of producing such materials com rising a plurality of elements in finely divi ed form.

An object of the invention is to facilitate the production of finely divided magnetic materials which are employed as cores for loading coils and other induction devices.

Another object of this invention is to enable production of magnetic materials in finely divided form from the elemental constituents of these materials.

A more articular object of this invention is to provlde a more desirable method than has heretofore been available for the preparation in iinely divided form of magneticy alloys comprising iron and nickel, iron and cobalt, or iron, cobalt and nickel together w with a third constituent such as manganese,

a metal of the chromium-molybdenum-tungsten `group or silicon.

The im rovement of the electrical and ma etic c aracteristics of iron-nickel, ironnic el-cobalt and iron-cobalt alloys by the addition of certain other constituents is well known ir the art. The addition of small quantities of chromium, molybdenum, tungsten manganese or silicon has been particu- 3 larly ever, the reduction to powdered form of alloys required for dust cores of magnetic compositions containing these elements has been found to be fraught with diiiiculty. The physical properties ofiron-nickel, iron-nick,-

el-cobalt and iron-cobalt alloys containing these elements are especially critical to the presence of impurities, such as sulphur and `oxygen' usually present in ferrous alloys. 4 Sometimes these alloys due to the quantity of impurities become hot-short, and consequently too brittle for lthe hot rolling operation 1n the method now in use which is hereinafter described. On the other hand, 5 if these impurities are not present in a quantity which produces the hot-short effect, ,the alloys are too tou h for pulverizing.

In the method now 1n use for the production of a dust core, the constituent elements 5 which comprise the alloy for the dust core advantageous in this respect. I-Iow-v are first melted together to form a homogeneous alloy. The alloy is then cast and the resulting 1n ot hot-rolled to the desired dimansions. s stated previously, if the alloy is hot-short, serious diiiicultv is encountered 1n th1s cperation. After the alloy has been rolled, 1t is placed in a ball mill or other means for reducing the strips to owdered form. In this o eration if the aliby is too tough, 1t cannot readily pulverized. Inasmuch as strains are produced in the allo gy the pulverizing, the powder is annealed: he powder is then insulated with a suitable material and subsequently pressed into cores. The cores are again annealed and are ready for use for coils.

According to one feature of this invent1on, an elemental constituent is alloyed with' the binarand ternary alloys of iron, nickel and coba t to produce a magnetic material in powdered form. The constituent and the alloy are pulverized to the desired degree of iineness. The two are mixed together and placed in a container which is subsequently l hermetically sealed. The container is heat- 75 ed to a temperature below the fusion oints of the alloy and the element but suiiiciently high to result in the substantial didusion of the element andthe alloy. The resulting -sintered mass is readily broken up into the desired pulverized form. This method obviates the difficulties encountered as a result of the physical characteristics of the ferrous alloys containing manganese, silicon or a metal of the chromium-molybdenum-tungsten group. The binary and ternary alloys of iror., nickel and cobalt may be prepared by the fusion method and after the pulverization mixed with the powder of a constituent or constituents of the chromium-molybdenum-tungsten group, manganese or silicon and heated in hermetically sealed containers at a temperature that produces substantial diffusion. The sintered mass may then be broken up, and made into cores Ias in the method now employed. Ternary alloys of iron, nickel and cobalt may be produced in powdered form by this method by mixing in owdered form two binary alloys or one inary alloy and the other element of the 100 alloy "or the three constituents'of the alloy and treating the mixture in a manner slmilar tothat described. f For exam le, to (pre are an allo com rising iron, nic el an co alt in pow ered orm, a mixture of an alloy corn- 'prlsing nickel and irpn and another comprising iron and cobalt, both of which are 1n powdered form ora mixture of' powdered alloy comprising iron and cobalt and powdered nickel or al mixture of powdered iron, nickel and cobalt',in their elemental state ma be employed.` ccording to another feature of this invention, the elemental constituents of the alloys desired may be mixed togetherin powdered form and heatedl to a temperature below the fusion points ofi'the lowest melting constituent and high enough for thel constituents to diffuse into each pther. f The sintered mass may then be broken up to the desired e ree of fineness., In this,l manner ironic elchromium, iron-nickel-niolybdenum, i/il'on-cobalt-nickel-tungsten alloys or any other binary, ternary ori quaternary magnetic alloy maybe produced in powdered form. The nature of this, invention is indicated by the accompanying drawing in which Fig. 1` represents 1n schematic form the steps involved in the preparation of magnetic alloys for dust cores 'from an element and a metal comprising one or more constituents and in which Fig. 2'shows schematically the process for theproduction of,'a ternary alloy in powdered yform from threeelemental constituents.' In Figs. l and 2, the'steps in the preparation of a comminuted alloy are indicated in boxes of solid black lines, while the usual subseguent operations `for producing the cores rom the pow ered dust are shown in the boxes of dotte lines. y

Two specific examples serve to demonstrate the procedure of this method. It is understood that' ,this ,invention is not restricted to lthe particular ,proportions stated, or to the details ot manipulations described, or to apparatus employed, or to the temperatures attained, or to the period of time of heating, or to the degree 'of fineness of the alloys or constituents used', all of these factors being merely 'given by :ivvay of illustration.

The rstfexample involving the produc y tion of 'a comminuted alloy comprislng iron, nickel' and molybdenum illustrates the methv od-,forf the preparation of a finely divided ally from a powdered metal comprising one or more elements and a powdered element.

The method of producing the finely divided iron+nickelmolybdenum alloy is shown schematically in Fig. 1. An alloy comprising ap-` proximately 80% nickel and the remainder chiefly iron is pulverized in an attrition mill orfother mechanical comminution agency to a powder line enough to pass through a 120- meshsleve. Powdered molybdenum obtained by el/ther pulverizing or chemical methods in a form finer than 120-mesh is mixed with the iron-nickel alloy in.l the proportions of 2 parts of molybdenum and 98 arts of ironnickel allo The mixture of t e iron-nickel alloy and t e molybdenum is placed in a container provided with a cover. At times, it is desirable to lace a small layer of iron filings on top ofp the mixture. This practice is particularly advantageous if the mixture occupies only a portion of the container. After the mixture is within the container, the cover is placed thereon. The junction between the cover and the container is sealed with a refractory cement or other sealing material. This latter/procedure affects the substantial hermetically sealing of the container for metallurgical purposes. It is t0 be understood, however, that the mixture may be placed in any instrumentality that will insure the substantial diffusion of the molybdenum and the iron-nickel alloy and prevent material contamination of the'resulting molybdenum-nickel-iron alloy. The mixture in the container is heated in the range between 800" C. to 1200 C. for a period of approxi- `mately twenty hours, the desirable temperapressed and annealed in the same manner as cores prepared by the fusion method. Cores containing iron-nickel-molybdenum alloys produced by this method have substantially the same magnetic and electrical characteristics asthose prepared from approximately the same amount of constituents by the fusion method. Cores containing ironnickel-chromium, iron-nickel-tungsten, ironnickel-manganese and iron-nickel-'silicon alloys in powder form as well as iron-cobalt and iron-nickel-cobalt alloys containing a third element are examples of magnetic alloys which lc'an be produced by this method.

The second example demonstrates the method for he preparation of an alloy in finely divided form from its elemental constituentsf. .,In the preparation of alloys from their elemental constituents, the method is substantially the same. or example, if an alloy of approximately the same composition as that prepared in the first example is de obtained in a finely divided state by pulver-V izing the rolled sheet, or casting as described above, for by chemical processes, such as electrolysis or in the case of nickel and iron from their respective carbonyls. The mixture is laced in a container which is subsequently ermetically sealed according to the procedure described in Example 1. Any instrumentality other than this specific a paratus may be employed that effects the substantial freedom from contamination of the elemental constituents and the resulting alloy and that facilitates the diffusion of the constituents with one another. The mixture is then heated for approximately twenty hours at a temperature below the fusion point of the lowest melting constituent and the resulting alloy but sufiiciently high to enable the constituents to diffuse into each other.- The temperature range found satisfactory for this alloy is between. 800 and 1200 C., a temperature of 900 C. being desirable. The rcsultant product after cooling is removed from the container and is rather easily broken in an attrition mill or other comminution means. This-alloy as well as others, such as ironnickelmol bdenum, iron-nickel-chromium, and iron-mckel-cobalt-molybdenum prepared by this method when placed in dust cores exhibits magnetic and electrical characteristics substantially similar to the corresponding alloys comprising the same quantity of constituents and prepared by the fusion method. This method may be applied to the production of other magnetic alloys, such as ironnickel tungsten, iron cobalt-molybdenum, iron-cobalt-nickel-manganese, iron nickelsilicon and the binary and ternary alloys of iron, nickel and cobalt. v

Intermediate steps not appearing in the specific examples described may also be employed without materially diverting from the scope of this invention.

What is claimed is: 1. A method of producing a magnetic material ,in finely divided form which comprises mixing a metal and an lelement in the desired proportions, said mental and said element being in a finely divided form, and heat-l ing said mixture ata temperature below the :fusion point of said metal and said element and sufiiciently high .to effect the substantial diffusion of said element and said metal.

2. A method of producing aI magnetic material in finely divided form in accordance with claim 1, in which the metal comprises iron and nickel and the element is silicon.

3. A method of producing a magnetic material in finely divided form in accordance l with claim 1, in which the metal comprises iron and the element is silicon.

4. A method of producing a magnetic material in finely divided form which comprises mixing a plurality of metals, said metals being in a finely divided form and heating said mixture at a temperature below the fusion points of said metals and sufiiciently high to effect the substantial diusion of said metals.

5. lA method of producing a magnetic material in finely divided form in accordance with claim-4, in which one of the metals comprises nickel and iron and another a member of lthe chromium molybdenum -tungsten group.

6. A method of producing a magnetic ma# 9. A method of producing a magnetic may terial in finely divided form in accordance withfclaim 4, in which one of Said metals comprises iron, another nickel and another manganese.

10. A method of producing a magnetic material in a finely divided form in accordance with claim 4, in which one of said metals comprises iron, another cobalt and another a member of the chromium-molybdenumtungsten group.

11. A method of producing a magnetic material in a finely divided form in accordance with claim 4, in which one of said metals comprises iron, another cobalt, and another manganese.

12. A method of producing a magnetic material in finely divided form in accordance with claim 4, in which `one of said metals comprises iron, another nickel and another cobalt.

13. A method of producing a magnetic material in finely divided form in accordance with claim 4, in which one of said metals comprises iron and nickel and another comprises iron and cobalt.

' 14. A method of producing a magnetic material in finely divided form in accordance vwith claim4, in which one of said metals comprises iron and nickel, another comprises iron and cobalt and another a member of the iron-nickel-cobalt group.

15. A method of producing a magnetic material in finely divided form in accordance with claim 4, in which one of said metals comprises iron. another cobalt, another nickel, and another a. member of the chromium-molybdenum-tungsten group.

16. A method of producing a magnet-ic material in finely divided form which comprises mixing an alloy and an elemental metal in the desired proportions, said alloy and said metal bein in a finely divided form,

and heating sai mixture at a tem A rature below the fusing oint of said a oy and said metal and su ciently high and for a riod sutliciently long toefl'ect substantial iffusion.

17. A methody of reducing a magnetic material in finely divided form which comprises mixing an alloy comprising iron and nickel and a metal of the tungsten-chromium-molybdenum group in the desired proportions, said alloy and said metal being in a finely divided form, and heating said mixture at a temperature below the fusing point of said alloy and said metal and sufliciently high and for a period suiiiciently long to eieet substantial diffusion.

18. A method of roducingla magnetic material in finely divided form which comprises mixing a metal comprising man anese with an alloy comprising iron and nic el in the desired proportions, said metal and said alloy being in a finely divided form and heating said mixture at a temperature below the fusin point of said metal'and said alloy and su ciently high and for a period sufliciently long to effect substantial diffusion. ,l

19. A method of producing a magnetic inaterial in finely divided form which comprises reducing an allo and an elemental metal to a finely divide form, mixing said alloy and said metal in the desired proportions, placing said mixture in a container, hermetically sealing said container, heating said mixture to a temperature below the fusion oint of said alloy and said metal and su ciently high to effect substantial diffusion, and reducin the resulting product to the desired finely divided form.

' 20. A method of producing a magnetic material in finely divided form in accordance with claim 19, in which the alloy comprises iron and nickel.

21. A method. of producing a magnetic material in finely divided form in accordance with claim 19, in which the alloy comprises iron, nickel and cobalt.

22. A methodof producing a magnetic materialin nely divided form which comprises mixing an allo comprising iron and nickel and a metal o the chromium-molybdenum-tungsfen group in the desired proportions, both said alloy and said metal being suflciently fine to pass throughma 120-mesh sieve, placing said mixture in "a container, hermetically sealing said container, heating said mixture to a temperature between 800 to 1200 C. for a period suicient for substantial diffusion, and reducing the resultifng product to the desired finely divided orm.

23. A method of producing a magnetic i material in finely divided form which comprises mixing an alloy comprising iron and nickel with manganese in the desired proportions, both said alloy and said manganese being sufiicientl fine to pass through a 120- mesh sieve, an placing said mixture in a container, hermetically sealing said conl0 tainer, heating said mixture at a tem rature between 800 to 1200 C. for a period suicient for the substantial completion lof diffusion, and reducing the resulting product to the desired finely divided form.

24. A method of producing a magnetic material in finely divided form which com'- prises mixing approximatelyy 96 to 98 prtsr' of an alloy comprising to 85% nickel. and the remainder chiefly iron with approxi- M mately 2 to 4 parts of ya metal of the chromium-molybdenum-tungsten group, both' said alloy and said metal being in avr form which is sufliciently-fine to pass through a 12p-mesh sieve, placing said mixture in a con- 85 tainer, hermetically sealing said container, heating said mixture at a temperature between 800 and 1200 C. for .fa period suicieiit for the substantial completion of diffusion, and reducin the resulting sintered mass to the desired nely divided form.

25., A method of producing a magnetic material iii finely divided form which comprises mixing approximately 96 to 98 parts of an alloy comprising 75% to 85% nickel 0l and the remainder chiefly iron with ap roximately 2 to 4 parts of manganese, both) said alloy and said manganese being in a form which is sufiiciently fine to ass through a 120-mesh sieve, placing sai mixture in a 100 container, hermetically sealing 'said container, heating said mixture atea temperature between 800 and 1200 C. for a period sufficient for the substantial completion of diffusion, and reducing the resultin sintered mass to the desired finely divided orm.

In witness whereof, we hereunto subscribe our names this 14th day of April, 1932.

EARLE E. SCHUMACHER. v'WILLIAM C; ELLIS. 

